Filin A A, Baru V, Epelbaum E, Krebs H, Möller D, Reinert P
Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Institut für Theoretische Physik II, D-44780 Bochum, Germany.
Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn, Germany.
Phys Rev Lett. 2020 Feb 28;124(8):082501. doi: 10.1103/PhysRevLett.124.082501.
We present a high-accuracy calculation of the deuteron structure radius in chiral effective field theory. Our analysis employs the state-of-the-art semilocal two-nucleon potentials and takes into account two-body contributions to the charge density operators up to fifth order in the chiral expansion. The strength of the fifth-order short-range two-body contribution to the charge density operator is adjusted to the experimental data on the deuteron charge form factor. A detailed error analysis is performed by propagating the statistical uncertainties of the low-energy constants entering the two-nucleon potentials and by estimating errors from the truncation of the chiral expansion as well as from uncertainties in the nucleon form factors. Using the predicted value for the deuteron structure radius together with the very accurate atomic data for the difference of the deuteron and proton charge radii we, for the first time, extract the charge radius of the neutron from light nuclei. The extracted value reads r_{n}^{2}=-0.106_{-0.005}^{+0.007} fm^{2} and its magnitude is about 1.7σ smaller than the current value given by the Particle Data Group. In addition, given the high accuracy of the calculated deuteron charge form factor and its careful and systematic error analysis, our results open the way for an accurate determination of the nucleon form factors from elastic electron-deuteron scattering data measured at the Mainz Microtron and other experimental facilities.
我们在手征有效场论中给出了氘核结构半径的高精度计算。我们的分析采用了最先进的半局部两体势，并考虑了在手征展开中对电荷密度算符的两体贡献，直至第五阶。将对电荷密度算符的第五阶短程两体贡献的强度调整到关于氘核电荷形状因子的实验数据。通过传播进入两体势的低能常数的统计不确定性，并估计手征展开截断以及核子形状因子不确定性带来的误差，进行了详细的误差分析。利用氘核结构半径的预测值以及氘核和质子电荷半径之差的非常精确的原子数据，我们首次从轻核中提取出中子的电荷半径。提取值为(r_{n}^{2}=-0.106_{-0.005}^{+0.007},,fm^{2})，其大小比粒子数据组给出的当前值小约(1.7\sigma)。此外，鉴于计算出的氘核电荷形状因子的高精度及其仔细且系统的误差分析，我们的结果为根据在美因茨微tron和其他实验设施测量的弹性电子 - 氘核散射数据准确确定核子形状因子开辟了道路。
